<!doctype quirks>
<title>CSS Test: Flex body in quirks mode</title>
<link rel="author" title="Aleks Totic" href="atotic@chromium.org">
<style>
html {
  margin:3px 6px 9px 12px;
  padding: 0px;
  background-color: green;
}
body {
  display: block;
  margin: 7px 11px 14px 23px;;
  padding: 0px;
  background-color: yellow;
}
</style>
Flex body in quirks mode should fill viewport except for margins.